WOLF BLITZER, CNN ANCHOR: Berned. Hillary Clinton laughs off Bernie Sanders' claim that she's not qualified to be president. He says she started it. Will they leave scars on the party?

On Trump's turf. He's ramping up his campaign to win his home state of New York and blasting Ted Cruz along the way. Tonight, he's warning that New Yorkers won't forget Cruz's disparaging comments about their values.

Lose with Cruz? As more top GOP officials reluctantly embrace the senator, are they privately admitting defeat for the party in the fall?

And on the lam. New video shows the missing Brussels bombing suspect as he fled the scene, ambling through the streets in his dark hat and white jacket. A top U.S. now official telling CNN exclusively why European nations have trouble tracking terrorists.

We want to welcome our viewers in the United States and around the world. I'm Wolf Blitzer. You're in THE SITUATION ROOM.

Tonight, the Democratic presidential race is taking an ugly detour from the high road. Bernie Sanders is arguing that Hillary Clinton isn't qualified for the presidency. He's accusing Hillary Clinton of making a similar claim about him and says he won't be beaten up.

As for Clinton, she took a spin on the New York subway today while her campaign accused Sanders of sinking to a new low. The Democrats trading barbs as they prepare to face off in CNN's Democratic presidential debate in Brooklyn one week exactly from today.

The Republicans also on the attack heading into the delegate-rich New York primary. Tonight, Donald Trump is out with a new video. He's blasting Ted Cruz for his now infamous remark about New York values.

Another major story we're following. There's new evidence now revealed in the hunt for the missing Brussels bombing suspect, surveillance video showing his route as he slipped away after terror attacks.

We have our correspondents, analysts and newsmakers. They're all following the news. We're also following the top stories, including a prominent Bernie Sanders supporter standing by to join us live. There she is, Congresswoman Tulsi Gabbard.

Up first, let's go to our senior Washington correspondent, Joe Johns.

Joe, you're in Philadelphia, where Bernie Sanders strongly defended his attack on Hillary Clinton's qualifications. What did he say?

JOE JOHNS, CNN SENIOR CORRESPONDENT: Wolf, Bernie Sanders went after Hillary Clinton twice in less than 24 hours with the kind of ferociousness we have seen more reserved for the Republicans.

While Hillary Clinton was trying to appear above it all, her campaign was fending off charges that they were the ones who started it.

SANDERS: I will not be hustling money from the wealthy and the powerful.

JOHNS: Sanders is not backing down from a fight he insists Clinton started.

SANDERS: I'm not going to get beaten up. I'm not going to get lied about. We will fight back.

JOHNS: Tensions coming to a boil, with Sanders launching a blistering critique of Clinton at a Philadelphia rally Thursday night.

SANDERS: Let me just say in response to Secretary Clinton, I don't believe that she is qualified, if she is through her super PAC taking tens of millions of dollars in special interest funds. I don't think you are qualified if you have voted for the disastrous war in Iraq.

JOHNS: Clinton today brushing off the criticism from her rival.

H. CLINTON: Well, it's kind of a silly thing to say, but I'm going to trust the voters of New York who know me and have voted for me three times, twice for Senate, once in the presidential primary. JOHNS: Both campaigns are looking to leverage the back and forth,

sending out fund-raising e-mails to supporters. The Clinton team calling Sanders' remarks a ridiculous and irresponsible attack. The Sanders campaign accusing the Clinton camp of getting nervous and launching a full-on attack before the New York primary.

Ahead of the April 19 contest in her adopted home state, Clinton today focused on her connections to New York.

H. CLINTON: I am so proud to have represented this state for eight years. I'm a proud New Yorker, and I want to be a good president for New York and for the rest of our country.

JOHNS: Engaging in some retail politics, riding the New York subway for two stops.

H. CLINTON: Do some people need to get off?

JOHNS: Along the way, she took a swipe at Sanders for incorrectly referring to the subway fare as tokens.

H. CLINTON: I think we changed when I was senator. I think it was my first term when we changed from tokens to MetroCards.

(END VIDEOTAPE)

[18:05:03]

JOHNS: Hillary Clinton was in Ohio today, as well as Colorado doing some fund-raising. Bernie Sanders expected to move up to New York again for more campaigning -- Wolf, back to you.

BLITZER: All right, Joe, thanks very much.

More fireworks for the Democrats tonight. This time, it's Bill Clinton who is generating some sparks with an angry finger-pointing response to protesters.

He was campaigning in Philadelphia, of course, in advance of that primary, which is a week after the New York primary. But it's a question that's dogged the Clintons about him signing the crime bill more than two decades ago. Black Lives Matters protesters came to his rally and tried to interrupt his speech. Let's watch.

(BEGIN VIDEO CLIP)

BILL CLINTON, FORMER PRESIDENT OF THE UNITED STATES: Oh, now wait a minute. Wait a minute.

Now you're screaming. So let's do another one. I don't know how you would characterize the gang leaders who got 13-year-old kids hopped up on crack and sent them out into the street to murder other African- American children. Maybe you thought they were good citizens.

She didn't. She didn't. You are defending the people who killed the lives you say matter. Tell the truth. You are defending the people who caused young people to go out and take guns. There was a 13-year- old girl in Washington, D.C., who was planning her own -- how would you do it?

Now, look at this. Look at this. That's not true. And the reason is they know it's true is they won't hush. When somebody won't hush and listen to you, that ain't democracy. They are afraid of the truth. Don't you be afraid of the truth. Don't you be afraid of the truth.

This doesn't necessarily have much to do with the central theme of this campaign here, but it just shows that he is still one of her best campaigners out there. But this is an issue that's not going away. Hillary Clinton certainly has been protested by some Black Lives Matters protesters as well. It's one of the issues in this campaign.

But one aide I talked to this afternoon said, Wolf, they are happy he's talking to these protesters and he's not engaging Bernie Sanders -- Wolf.

BLITZER: Hillary Clinton, as you know, she was secretary of state for four years. She was a U.S. senator from New York for eight years. Do you think she's qualified to be president of the United States?

GABBARD: Wolf, this whole back and forth I think is really getting hyped up a lot more by the media.

And really what I hear from people along the campaign trail and what I know the American people are concerned about is about who is right and wrong on issues that are important to them. I can see why the Clinton campaign is getting nervous. Bernie has won seven out of the last eight states. He's clearly got momentum as he gains more support in the states that are coming up. But really what it comes down to and what is important to talk about

in this election is the differences between the two candidates. And you and I have spoken before specifically on Secretary Clinton's tenure as secretary of state, as U.S. senator, and the track record that she has in particular on these foreign policy issues.

So when voters are looking at in these upcoming states, what are the differences, some key distinctions that are important to note are beginning with the Iraq War. Secretary Clinton either didn't do her homework properly or she didn't have the foresight and judgment to know how that war would end up, and she voted for it. Bernie Sanders voted against it.

(CROSSTALK)

BLITZER: Let me interrupt for a second, Congresswoman. Am I hearing you? Do you agree then with Bernie Sanders that because of that vote on the war, because she takes money from Wall Street, because she supports some of these free-trade agreements, she is not qualified to be president of the United States? The media didn't say that. Senator Sanders said that.

GABBARD: Again, Wolf, I think it's important that the voters are going to make this decision themselves. And they're going to make this decision based on who they believe will be our president and commander in chief and who will do the best job at that.

And that's why it's important to make these clear distinctions between Hillary Clinton and Bernie Sanders on these issues of war and peace, on these issues really that will impact who will lead our country as our next commander in chief.

And, as I mentioned, it's not just about Iraq. It's about what happened after that. It's about her decision as the architect and champion for the military overthrow of Gadhafi in Libya that resulted in a failed nation and chaos and loss of life and a stronger ISIS and al Qaeda, and now with the current war in Syria, where Secretary Clinton supports continuing this regime change, interventionist war.

[18:10:11]

Bernie Sanders opposes it and has promised to end it. She's promised to continue it and continue to escalate it with the no-fly zone, without providing any details on exactly how many U.S. aircraft will be necessary to implement that no-fly zone. How will it be effective?

How many U.S. ground troops will be required to enforce that so-called safe zone or no-fly zone? What will happen if a Russian plane, for example, violates that no-fly zone? There's so many questions on what she's proposing to do on this current-day war in Syria that have yet to be answered, and I encourage you to ask her those questions in the debate that you are going to be moderating coming up in New York.

BLITZER: I'm sure we will.

But it sounds like you are making the case that you don't believe she's qualified to be president of the United States. Let me rephrase the question and ask you this. Let's say she gets the Democratic nomination. Will you support her?

GABBARD: I am focused on supporting Bernie Sanders in winning this Democratic nomination. We will cross that bridge if and when we get there.

But I am working hard to make sure that voters in these states that are coming up and voting in the coming days are informed about the differences so that they can make that best decision for themselves.

BLITZER: It's really hard, I see, for you to say those words, yes, I would support her if she's the Democratic nominee. You are a Democrat. So you really have a serious problem with Hillary Clinton, right?

GABBARD: Well, I have serious issues with the track record and the positions that she's taken on -- in particular as it relates to foreign policy and the decisions that she has made that have cost our country trillions of dollars, that have cost our country thousands of lives.

My brothers and sisters in uniform who I served with who never made that trip home on, whose families are still home grieving the loss of their loved ones, there are very real consequences to this election. It's not just about a horse race or who is going to pick up the most points.

It is about the very real consequences of this decision that's before the American people, and why it's so important for us, all of us, the media, the American people, to really talk about and examine carefully what it is that she is proposing, what's it is that Bernie Sanders is proposing, where are the differences in that and what's the consequences of those positions that they have taken, in particular on these issues of war and peace.

BLITZER: And this is an issue that is very, very personal for you. You served. You are a U.S. military veteran, served in the war in Iraq and you saw what was going on. I know you take that, that vote that she had going forward with the war, obviously, very, very seriously. Bernie Sanders opposed that war.

Let's talk about Bernie Sanders as a Democrat. You are a Democrat. You're the Democratic congresswoman from Hawaii. He's not a Democrat, although he's running for the Democratic presidential nomination. So far, it doesn't look like any of his Democratic colleagues -- he's an independent senator from Vermont -- but none of the Democrats in the Senate have endorsed him in the Senate.

He's got some supporters in the House of Representatives like you, but not in the Senate. Why do you believe no Democratic senator has endorsed him?

GABBARD: That's a good question.

I think that there's a lot of fear, unfortunately, that drives decisions that are being made in Washington. Fear against going against the establishment. Fear against what going against the so- called Clinton machine will bring upon them.

I'm not going to speak for any particular senator or make presumptions about why they are making their own decisions. But I think for those who have endorsed Bernie Sanders, whether they are elected officials or people out in these communities, people who I have met who are really excited and hopeful about the opportunity to really empower the people again and take government and those -- out of the hands of those very few powerful, very wealthy and those very few who have influence and really open the doors wide up, so that we're focusing on exactly who we are supposed to be serving as public servants, as elected officials and remember that.

Remember who hired us to do our jobs.

BLITZER: All right, Tulsi Gabbard, I want you to stand by. We have more to discuss. We will take a quick break.

Much more with the Democratic congresswoman from Hawaii, an Iraq War veteran, right after this.

(COMMERCIAL BREAK)

[18:18:49]

BLITZER: We're back with Congresswoman Tulsi Gabbard of Hawaii. She's a leading supporter of Senator Bernie Sanders' campaign.

Congresswoman, as the Democratic race grows more contentious, Bernie Sanders, as you know, he is claiming Hillary Clinton is not qualified to be president of the United States. She's raising questions about him, pointing to that "New York Daily News" interview with the editorial board in which he didn't know what legal authority he would have on the Federal Reserve, the Department of Treasury, to go ahead and break up Wall Street, to break up those big banks.

He's getting a lot of criticism for that. What's your reaction?

GABBARD: Well, Bernie Sanders has laid out a very clear plan on exactly what he will do in order to reform Wall Street and bring back some sensibility to our financial industry.

And he has detailed exactly what that would be. There have also been articles and experts and economists who have defended Bernie Sanders' interview there, who have said exactly what he laid out that he will do and the distinctions that he made.

I think an important difference between Secretary Clinton and Senator Sanders is on the reinstatement of the Glass-Steagall Act. This is one of the key elements of Bernie Sanders' plan that he's laid out, which is to reinstate a 21st century Glass-Steagall Act, something that would separate the risky investment banking practices that were really the cause of this 2008 crash in our economy from the commercial banking that consumers rely on for their day-to-day lives and their work. [18:20:20]

This is something that Secretary Clinton has refused to support. And so it actually doesn't surprise me that rather than really talking about the substance and the differences between their plan and how they will reform Wall Street, instead, they're trying to raise things that really don't exist, saying that Senator Sanders doesn't have a plan, when he talks almost every day about what his plan is.

BLITZER: Do you believe, Congresswoman, that Bernie Sanders' best political interest right now is to really go negative against Hillary Clinton?

GABBARD: I actually disagree that Senator Sanders is going negative.

I think that he is doing something that I think he will probably continue to do. And that is raise the differences, and raise the contrasts between he and Secretary Clinton, both on their record as well as on their positions on different issues.

You know, he feels really strongly about a lot of these things, including Wall Street reform and how to make sure that the financial industry is best serving a stable economy and the American people. And I imagine that he will continue to raise those differences, so people know before they go and cast votes in New York, in Pennsylvania, in California and all these other states that have yet to vote, so they know exactly who they are getting.

BLITZER: But it's pretty negative when he says she's not qualified to be president. It doesn't get a whole lot more negative than that. Right?

GABBARD: He's raising -- I think it's important that you look at the context of the points that he's raising, and you could say the very same things about Secretary Clinton and what she's saying and her surrogates are saying about Senator Sanders.

If you look at the substance of what Senator Sanders is talking about, it's about raising the differences and informing people about how he and Secretary Clinton disagree on some pretty key and important issues, whether it be Wall Street reform, whether it be the Iraq War, whether it be the current war, the regime change, unnecessary war happening in Syria that's causing so much human suffering and strengthening our enemy in ISIS and al Qaeda.

There are clearly differences. And I think it's important actually for Senator Sanders to continue contrasting his positions with Secretary Clinton's positions, because there are real differences that are there.

BLITZER: Congresswoman Tulsi Gabbard, thanks very much for joining us.

GABBARD: Thanks, Wolf. Aloha.

BLITZER: As I told Democratic Congressman Hakeem Jeffries in the last hour -- he's a supporter of Bernie -- he's a supporter of Hillary Clinton's -- Hillary Clinton is lucky to have him. Bernie Sanders is lucky to have you on his team as well.

Thank you to both of you.

An important note. Hillary Clinton and Bernie Sanders, they will face off one week from tonight for CNN's Democratic presidential debate in Brooklyn. I will be the moderator. Please be sure to join us one week from tonight, April 14, 9:00 p.m. Eastern live right here on CNN.

Just ahead, Donald Trump's New York state of mind, why he's scrapping plans to leave the state any time soon.

And Bill Clinton's very angry response today to Black Lives Matter protesters, what's going to be the impact?

(COMMERCIAL BREAK)

[18:27:58]

BLITZER: Tonight, Ted Cruz is reaching out to New York's Jewish community, helping children make matzah at a bakery.

At the same time, Donald Trump is reminding New Yorkers that Cruz attacked their values. The GOP front-runner now is gearing up for what is likely to be a contested convention and a brutal battle over delegates.

Let's go to CNN's political reporter, Sara Murray. She's in New York for us.

Sara, Trump is battling for New York, but also looking beyond the primaries. What's the latest?

The Trump campaign definitely wants to go into Cleveland with 1,237 delegates. They want to avoid a floor fight. But they're doing everything they can to prepare just in case things don't go quite as planned.

(BEGIN VIDEOTAPE)

DONALD TRUMP (R), PRESIDENTIAL CANDIDATE: This is home. It's great to be home. We love New York.

(CHEERING AND APPLAUSE)

MURRAY (voice-over): Donald Trump is clearly in a New York state of mind.

TRUMP: I love these people. These are my people. Yes!

(CHEERING AND APPLAUSE) MURRAY: Campaigning in his home state, Trump is scrapping a California press conference scheduled for later this week and abandoning plans to appear at this weekend's Colorado convention.

The billionaire businessman is trying to put a stinging loss in Wisconsin in the rear-view mirror and launch a more disciplined delegate hunt.

Today, Trump appeared to expand the role of a key hire, Veteran GOP Paul Manafort, to oversee delegate operations, as well as Washington outreach. Now that the race has shifted to New York, this dig at New York values:

SEN. TED CRUZ (R-TX), PRESIDENTIAL CANDIDATE: I think most people know exactly what New York values are.

UNIDENTIFIED FEMALE: I am from New York. I don't.

CRUZ: Well, you're from New York, so you might not.

MURRAY: May come back to bite.

TRUMP: I have got this guy standing over there looking at me, talking about New York values with scorn in his face, with hatred, with hatred of New York. So, folks, I think you can forget about him.

MURRAY: Cruz is lagging in third place in the latest New York polls. And the state may prove to be unfriendly territory.

UNIDENTIFIED MALE: Ted Cruz has no business being in the Bronx. This is an immigrant community.

But Cruz is fighting back, turning the knives on Trump and painting him as a not-so-secret New York liberal.

[18:30:11] CRUZ: Our friends in the media tell us that Donald Trump is unstoppable in New York state. Oddly enough, our friends in the media are very comfortable with a New York liberal who has supported Andrew Cuomo and Hillary Clinton and Chuck Schumer for decades.

MURRAY: All while John Kasich and the super PAC supporting him pile on against Ted Cruz.

UNIDENTIFIED MALE: When you smear New York values in Iowa for votes, we remember that, too. Now you come here and conveniently say you love New York.

MURRAY: Cruz also made a late day stop at a matzo bakery for children.

Kasich is going for the ultimate Empire State pander, stopping by a deli in the Bronx and saying he'd consider inviting former New York Yankee Derek Jeter to join the ticket. GOV. JOHN KASICH (R-OH), PRESIDENTIAL CANDIDATE: People say, "If you

win, who's going to be your vice president?" Somebody that I would have under consideration, Jeter.

(END VIDEOTAPE)

MURRAY: Now as the race moves to New York, Donald Trump is hoping to pick up all the delegates here. There are 95 at stake. You can see why they're hunkering down here in the state. So far, though, no public schedules for Donald Trump today, and nothing that's been released for tomorrow -- Wolf.

BLITZER: All right. We'll see what they do. All right. Thanks very much, Sara Murray.

Gloria, Donald Trump is turning his focus to the campaign in New York state, rather than California, at least for now. California isn't until early June. He's moving rallies here, releasing this Instagram video. Watch this.

(BEGIN VIDEO CLIP)

SEN. TED CRUZ (R-TX), PRESIDENTIAL CANDIDATE: Everyone understands that the values in New York City focus around money and the media.

DONALD TRUMP (R), PRESIDENTIAL CANDIDATE: I saw something that no place on earth could have handled more beautifully, more humanely than New York.

GRAPHIC: New York values are American values.

(END VIDEO CLIP)

BLITZER: "New York values are American values," it said. What's his strategy here?

GLORIA BORGER, CNN CHIEF POLITICAL ANALYST: Yes. First of all, I think that's a -- you know, it's a great video. It clearly -- you have to expect that Trump is going to use the New York values thing -- theme.

I think what he's trying to do by not, you know, going to Colorado or California and focusing on New York now is to try and reduce Cruz to getting zero delegates out of New York. New York has 95 delegates. If he keeps Cruz below 20 percent statewide, and in all congressional districts, he comes away with nothing. And I think, you know, Trump understands that this is now a delegate fight. And this is the place where he can really rack them up. So why not stay and make sure that he does it?

BLITZER: Jeff, Rudy Giuliani said today he will vote for, not necessarily endorse, but he will vote for Donald Trump in the New York Republican primary. Giuliani telling "The New York Times," doesn't agree with Trump on mass deportations or immigration, but he did say he was the best choice right now.

What does that tell you about this, insisting it's not an official endorsement, but he would vote for Trump?

JEFF ZELENY, CNN SENIOR POLITICAL CORRESPONDENT: It tells us, look, there aren't that many options here for a lot of New York Republicans. And largely because of what Ted Cruz said back during those -- the campaigning in Iowa about New York values.

Rudy Giuliani is not going to support, endorse or vote for someone who questioned New York values. So it's kind of -- he's kind of holding his nose a little bit here and saying, "I'm going to vote for Trump. I don't want to endorse him. I don't want to sort of support all of his ideas or be saddled with that," but he certainly wants to send a signal that he's supporting Trump.

And he also said that he believes that Trump will get over 50 percent of the delegates -- or over 50 percent of the vote, excuse me, which means all of the delegates here.

So there aren't that many options if you want to go with a winner in New York. Donald Trump is probably your best option. And that's in mind what's going on in Giuliani's mind.

BLITZER: Ryan, I want you to listen to what Senator Ted Cruz just told our Dana Bash. Listen to this.

(BEGIN VIDEO CLIP)

DANA BASH, CNN SENIOR POLITICAL CORRESPONDENT: Senator, thank you so much for sitting down with me.

CRUZ: It's great to be with you.

BASH: I'm sure you've seen this.

I'm glad you're laughing, because "The New York Daily News" gave you a warm welcome. They actually gave you some helpful hints, to take the "F" train and "U" train.

CRUZ: They're very helpful.

BASH: Very helpful.

In all seriousness, you know, when you saw this...

CRUZ: I laughed out loud. Look, I have never been popular with left- wing journalists or tabloids. And frankly, that's not my target audience.

[18:35:02] You know, I'll tell you the energy and support we're seeing, we just did a wonderful gathering here. I came to Brooklyn and baked some matzo and then just spoke with a Russian Jewish community, and the orthodox community and Hassidic Jewish community. And the energy and enthusiasm we had here today was tremendous.

(END VIDEO CLIP)

BLITZER: All right. So, Ryan, what do you think? He's campaigning in New York. The polls show he's in third place behind Kasich, obviously behind Trump. Do you think he's got a shot of doing anything in New York? A realistic shot?

RYAN LIZZA, CNN POLITICAL COMMENTATOR: The welcome to New York from the tabloids to Ted Cruz. He benefits from a couple of things. One, low expectations. Donald Trump is the overwhelming favorite in New York, and Ted Cruz has a couple of goals.

One, keep Donald Trump under 50 percent, because you get an extra pack of delegates if you break 50 percent. But then remember, it's congressional district by congressional district. And New York is a big state. Not everyone is a New York City liberal in New York. There are plenty of conservatives.

And he's just going to do a very targeted, strategic campaign, district by district, keep Donald Trump under 50 percent and win some of those district-level battles. So -- and he benefits from low expectations. At the end of the day Ted Cruz is not going to get a majority of the delegates by June 7. He's not going to go into the convention with a majority of the delegates. The whole game is to keep Donald Trump under 1,237. And so that's his strategy in New York.

BLITZER: Don Lemon, Bill Clinton, as you know, he clashed today with some Black Lives Matter protesters in Philadelphia. Really got angry at them. The protesters were critical of his 1994 crime bill. What do you think of that engagement he had with them? We've all seen the video by now.

DON LEMON, CNN ANCHOR: Well, I think it's -- this is why many people call, you know, the former president a brilliant politician, because of the way he engages people, the way he explained himself.

Listen, he has said it was a mistake, the way the bill was written, that it -- and admits that it did send African-American and Hispanic people, especially men, to jail more than any other segment of the population.

But he engaged with the protesters, and what I thought -- what I thought he did -- no one is excusing what he did. He's not even excusing the bill. Hillary Clinton is not excusing the bill. I asked her about it during our Flint debate.

But what he did so brilliantly was he explained to people the circumstances around signing the bill and what was happening back in 1994. The crime problem that we had. The crack epidemic. The epidemic that's happening on the streets in real time and that there were, as a representative said from New York, earlier on your show that there were members of the Congressional Black Caucus and other very prominent African-Americans who supported the 1994 crime bill. Hindsight is 20/20. It turned out to not be such a great bill, but at

least he explained it. So I think that he was brilliant in his explanation; but no one is, you know, forgiving him, at least for having signed it or at least, you know, letting him off the hook, I should say, is a better term.

BLITZER: All right. Everybody stand by.

Important note to our viewers: You can see Dana Bash's full interview, by the way, with Senator Ted Cruz later tonight on "ERIN BURNETT: OUTFRONT." That starts at the top of the hour.

Don Lemon will be back with much, much more, 10 p.m. Eastern on his program, "CNN TONIGHT."

Remember, CNN's Democratic presidential debate is in Brooklyn exactly one week from tonight. Please be sure to join us: April 14th, 9 p.m. Eastern, only here on CNN.

Just ahead, what can Republicans expect in Cleveland? An insider who played a major role in the last contested GOP convention is dishing out what it takes to win over delegates, and it isn't pretty.

And how did police in Brussels lose the trail of an airport attacker? CNN is talking exclusively to a top U.S. terror official. And new video is released of the suspect's escape.

(COMMERCIAL BREAK)

[18:43:27] BLITZER: A lot of Republicans right now, they're wringing their hands wondering what to expect if the July convention in Cleveland winds up being contested. Some party veterans know firsthand what it's like to see a bare-knuckle brawl over delegates play out on the convention floor and behind the scenes.

Our chief political analyst Gloria Borger sat down with a longtime power player in the GOP, who was at the last contested convention 40 years ago.

(BEGIN VIDEOTAPE)

BORGER (voice-over): After millions of votes, dozens of contests and heaps of mud flung along the way, the Republican presidential race has a bit of everything. Except a nominee.

CRUZ: We will win a majority of the delegates.

BORGER: The last time a contested convention happened was in 1976, when former California Governor Ronald Reagan was the outsider, challenging the president, Gerald Ford. Both men claimed to have the votes heading into the convention, but nobody was sure. Not even Jim Baker, who was then Ford's top delegate hunter.

JIM BAKER, WORKED WITH GERALD FORD CAMPAIGN: We had no assurance whatsoever that he would get the majority of votes necessary to be nominated. BORGER: But he did, winning the nomination and earning Baker

headlines. But it was far from easy.

RONALD REAGAN, FORMER PRESIDENT OF THE UNITED STATES: Mr. President...

BAKER: Governor Reagan -- Ronald Reagan almost knocked off an incumbent Republican president. We had to get in there and scramble for it and fight for it.

[18:45:01] BORGER: So as Donald Trump gets ready to rumble at the convention, Baker has little sympathy for the argument that, if Trump is closest to the finish line going in, he should be declared the winner.

TRUMP: It's mathematically unfair.

BORGER: Is that the way the process works?

BAKER: Well, that's a very good political argument for him to make but that's not actually the way the process is supposed to work.

UNIDENTIFIED MALE: Twenty votes for our fellow Texan.

BAKER: It's supposed to work in a vote or series of votes by the delegates on the floor of the convention. They select the nominee. It is, after all, a party's nominating convention.

BORGER (voice-over): The good news for Trump is that his supporters, like Ronald Reagan's 40 years ago, are diehard.

BAKER: Reagan had the benefit of the movement. I mean, his delegates, were really committed to what he stood for.

BORGER (on camera): Just the same way Trump's delegates are very committed to Donald Trump as the outsider.

BAKER: Provided Trump can get them selected as delegates and not have his delegate slots filled by a Kasich or Cruz person.

BORGER (voice-over): In other words, just winning the most delegates on primary nights is not enough.

WOLF BLITZER, CNN ANCHOR: Another win for Donald Trump.

BORGER: Winning states is one thing, but keeping your state delegates is another entirely. Not only on first ballot but hanging on to them if there are multiple votes, leaving delegates free to roam. Even defect. And that's where Trump's anti-establishment campaign is playing catch-up.

(on camera): If you were running the Trump delegate selection process now, what would you be doing?

BAKER: Well, I think they need to be ramping up a sophisticated delegate selection process. I'm not sure that they've been paying very much attention to their ground game.

BORGER: So, how do you keep track of it?

BAKER: What you have to do, you have -- first of all, you need to know everything there is to know about a potential delegate or a delegate. Most important thing to know is what turns them on, what turns them off, what they believe in, what they favor, what they disfavor, who they are sleeping with, the whole schmeer, OK?

You make a point to learn everything you can about each delegate. And then you just massage that delegate, you stay in touch with them. You work 'em, protect them to keep them from being stolen by the other side. It's a zero-sum game, and as people say all the time, it ain't bean bag.

BORGER (voice-over): With very few rules.

BAKER: Now, you've got to be very careful. You can't buy votes.

BORGER (on camera): So, what can you do?

BAKER: Well, there's some things you can do, and, of course, we can't -- we took great advantage of it in 1976 ahead of the party was the president of the United States.

BORGER: That helps.

BAKER: Yes, that helps a lot. There was a dinner for the queen of England, OK? So you have -- get an uncommitted delegate, invite him to the White House for a state dinner for the queen of England. You don't think you have a good chance of getting his vote? You have a good chance of getting his vote.

BORGER: Did you?

BAKER: But it was -- yes, we did. I bet I went to more state dinners than anybody in the Ford administration with exception of Betty and Gerald Ford.

BORGER: And some delegates brazenly asked for favors, some crossing the line.

BAKER: We got a lot of inappropriate requests and there are some outrageous ones like jobs, federal jobs.

BORGER (on camera): Federal jobs?

BAKER: Yes, federal jobs. If I'm not mistaken, there was a request to lay off a relative of one of the delegates who had been prosecuted for federal crime. I mean, things like that.

BORGER (voice-over): And proper requests aside, what's to stop a few friendly plane rides to Mar-a-Lago, or a hunting trip --

BAKER: The game wasn't only played on our side. It was played on their side, too. We just had some better inducements we could offer.

GERALD FORD, FORMER PRESIDENT: America is at peace.

BORGER: Still, it was close when it came to a head on the convention floor, Ford beat Reagan outright by just 117 votes.

RONALD REAGAN, FORMER PRESIDENT: We must go forth from here united.

BORGER: But this fight could be more bitter and last longer. And Baker warns that if it does, and the rules start changing in the middle of the game, there could be hell to pay, for the entire Republican party.

BAKER: If you have a candidate who is within 100 or 150 delegate votes of getting the majority and you start changing the rules to screw the candidate out of the nomination, I think you're going to get -- you're going to buy yourself some grief. You're going to buy yourself some grief in the general election, because his supporters, all of whom thought they were voting for significant change might stay home.

(END VIDEOTAPE)

[18:50:05] BORGER: And, Wolf, one big difference between now and 1976 is that while that was the tough fight, Reagan gave a great speech at the convention endorsing Ford and calling for party unity. And it's kind of hard right now for me to imagine either Trump or Cruz doing that this time around. And while we're talking about the convention, Wolf, today, the Trump campaign officially stepped up its delegate strategy with its newly appointed convention manager Paul Manafort who, by the way, worked for none other than Jim Baker at the 1976 convention.

So, Wolf, history has now come full circle.

BLITZER: As you know, Gloria, first of all, great piece you just did.

BORGER: Thanks.

BLITZER: But as you know, a lot of people think this may be a little late now to start that new effort to get the new delegates for the Trump campaign.

BORGER: Right.

BLITZER: The Cruz campaign has had a very strong ground game now for months.

BORGER: I think they do have an advantage. And I think that's what Jim Baker was pointing out. I mean, while he speaks very highly of Paul Manafort, he said, look, you know, you got to get in the game early. It's a very complicated game. It's 3D chess. You've got to figure out where people are not only on the first ballot, but beyond.

And you have to know who your people are and who you can depend on. And when you're an outsider, as Reagan was, and you've run as an anti- establishment candidate, it's kind of hard, because the people who go to the convention, Wolf, are party people. And they're not about sending messages or anything else like that. They're about winning. And they're going to go with the candidate whom they believe can beat the Democrat -- Wolf.

I just want to let our viewers know, Paul Manafort is going to be a guest on CNN's "NEW DAY" tomorrow morning. Check that out, an important interview coming up.

And, by the way, CNN takes you inside the Reagan revolution and the legacy of the president defined an era. Be sure to watch the original series "THE EIGHTIES". That's tonight, 9:00 p.m. Eastern, only here on CNN.

Just ahead, surveillance cameras captured a fugitive terror suspect leaving the scene of the Brussels attacks. The video and the mystery, when we come back.

(COMMERCIAL BREAK)

[18:56:41] BLITZER: Police have released extensive new video of the missing suspect in the Brussels airport terror attack. They're appealing for information about the mysterious man wearing a dark hat and a light jacket. They now know the route he took after fleeing the carnage, but they apparently don't have a clue as to where he is right now.

Let's bring in our justice correspondent Pamela Brown.

Pamela, you had a chance to seek with a top U.S. official about the difficulty in tracking these terror suspects. What did he say?

PAMELA BROWN, CNN JUSTICE CORRESPONDENT: That's right, Wolf.

Director Chris Piehota of the Terrorist Screening Center said in an exclusive interview that Europe could be more aggressive in tracking terrorists by routinely using U.S. watch lists when potential terrorists try to cross European borders.

(BEGIN VIDEOTAPE)

BROWN (voice-over): Tonight, new surveillance video emerging of one of the suspected Brussels terrorists still on the run as the head of the U.S. terror watch list, Christopher Piehota tells CNN exclusively most European countries are not taking full advantage of U.S. tools that help screen terrorists.

CHRISTOPHER PIEHOTA, DIRECTOR, TERRORIST SCREENING CENTER: It's concerning that our partners don't use all of our data. We provide them with tools. We provide them with support.

I would find it concerning that they don't use these tools to help screen for their own aviation security, maritime screening, border screening, visas, things like that for travel. We find it concerning.

BROWN: Making things even more difficult, European countries maintain their own individual terrorist watch lists, which each have different privacy standards, preventing them from sharing some suspect names with the U.S.

(on camera): In Europe, there are cases where perhaps information wasn't shared about someone because of privacy laws. How does that impact the terror watch lists?

PIEHOTA: It impacts the terror watch lists in a way that our sharing may not as broad or as inclusive as it could be.

BROWN (voice-over): Director Piehota fears the missing terrorist like the missing Brussels suspect could slip into the U.S.

PIEHOTA: There are many that we do know about. And unfortunately is there are some that we do not know about. We make sure that we know as much as we can. And we take that information and we use it the best we can to minimize threats to our communities. But we can't know everything all the time.

BROWN: Piehota says to get on the watch list, there must be reasonable suspicion someone has ties to terrorism. No one can be added based on their religion, as Republican presidential front-runner Donald Trump has proposed.

(on camera): Is that even possible? Can you do that?

PIEHOTA: That's a policy decision that I wouldn't be able to comment on.

BROWN: Could you ban someone because of their ethnicity or religion?

PIEHOTA: No watch listing activity is connected based upon race, religion, or any other protected right. There has to be a certainly level of derogatory information particularized to that individual that would warrant their watch listing. Being of a certain national origins or religous affiliation is not grounds for watch listing.

BROWN: And Piehota says U.S. citizens make up only half a percent of the watch listing population. Meantime, European officials have acknowledged gaps in coverage and communication following the Brussels attacks. But some European officials don't want border checks based on privacy grounds. It's a debate the European parliament is taking up this month -- Wolf.

BLITZER: Sure it is. All right. Thank you very much. Good report, Pamela Brown, working the story for us.

That's it for me. Thanks very much for watching. I'm Wolf Blitzer in "THE SITUATION ROOM." "ERIN BURNETT OUTFRONT" starts right now.